Sabot for sub-calibre projectile

ABSTRACT

A sabot for locating a finned missile in a rifled gun barrel, consisting of a rear sealing ring, an intermediate wedge unit and a front petal unit. The sealing ring and wedge unit have peripheral grooves to slidably fit a rifled barrel and the petal unit has a smooth periphery for sliding engagement with lands of the rifling. The petal unit and the wedge unit each consists of a set of separable complemental segments and the two units have complementally frusto-conical adjacent end faces so that the wedge segments are urged outwardly and the petal segments inwardly by a forward axial force on the sealing ring.

United States Patent [1 1 Eyre et a1.

[ June 12, 1973 SABOT FOR SUB-CALIBRE PROJECTILE [75] Inventors: FrankW. Eyre, Montreal, Quebec;

Fergus M. Groundwater, St. Lambert, Quebec, both of Canada [73]Assignee: The United States of America as represented by the Secretaryof the Navy, Washington, DC.

[22] Filed: July 24, 1970 [21] Appl. No.: 58,027

52 us. Cl. 102/94, l02/D IG.'7 [51] Int. Cl. F42b 13/16 [58] Field ofSearch 102/93, 94

[56] References Cited UNITED STATES PATENTS 3,262,391 7/1966 Shober102/93 2,699,094 l/l955 Musser 102/93 X 3,107,615 10/1963 Brady..lO2/93X Primary Examiner-Robert F. Stahl AttarneyR. S. Sciascia and J.A. Cooke [57] ABSTRACT A sabot for locating a finned missile in a rifledgun barrel, consisting of a rear sealing ring, an intermediate wedgeunit and a front petal unit. The sealing ring and wedge unit haveperipheral grooves to slidably fit a rifled barrel and the petal unithas a smooth periphery for sliding engagement with lands of the rifling.The petal unit and the wedge unit each consists of a set of separablecomplemental segments and the two units have complementallyfrusto-conical adjacent end faces so that the wedge segments are urgedoutwardly and the petal segments inwardly by a forward axial force onthe sealing ring.

7 Claims, 4 Drawing Figures PMENTED 313%279 INVENTORS Frank W. EyreFergus M. Groundwafier 1 SABOT FOR SUB-CALIBRE PROJECTILE This inventionrelates to new and useful improvements in sabots for locatingsub-calibre projectiles or missiles in gun barrels and although the useof the invention is not limited to any particular type of projectile, itespecially concerns itself with the locating of finstabilized missileslaunched from rifled gun barrels.

In order to increase the muzzle velocity and/or the altitude or range ofperformance of guns, it is customary in the art to use sabotedsub-calibre shells or missiles. Such sub-calibre shells may be eitherfinstabilized or spin-stabilized, but it is undesirable to spin a finnedmissile at high rates.

It is the principal object of the invention to provide an improved sabotwhich may be effectively used to transfer gun gas load to a sub-calibremissile in a rifled gun barrel without imparting any excessive amount ofspin or rotation to the missile, thereby substantially avoiding spinproblems and permitting a significant increase in the velocity and rangeor altitude of the gun.

Another object of the invention is to provide a sabot which is whollycompatible with the mechanical loading system of conventional guns andwhich functions effectively in new as well as in worn gun barrels.

With the foregoing more important objects and features in view and suchother objects and features which may become apparent as thisspecification proceeds, the invention will be understood from thefollowing description taken in conjunction with the accompanyingdrawings, in which like characters of reference are used to designatelike parts and in which:

FIG. 1 is a perspective view of a finned missile equipped with a sabotin accordance with the invention;

FIG. 2 is an enlarged fragmentary view, partly in side elevation andpartly in longitudinal section, of the missile and sabot thereon; I

FIG. 3 is a fragmentary perspective view showing serrated interfaces ofthe segments; and

FIG. 4 is a fragmentary perspective view of one of the grooved wedgesegments.

Referring now to the accompanying drawings in detail, the generalreference numeral in FIG. 1 designates a conventional finned missile ofsub-calibre for use in a rifled gun barrel, wherein the missile body 11is substantially smaller in diameter than the gun barrel and the fins 12on the rear end portion of the missile body porject radially to asufficient extent as to ride along lands of the barrel rifling to assistin stabilizing travel of the missile through the barrel. The improvedsabot of the invention is positioned on the missile body 11 and isdesignated generally as 13.

The sabot 13 consists of three main components, namely, a rear sealingring 14, an intermediate wedge unit 15, and a front petal unit 16. Inaddition, a washer 17 may be provided between the units l5, 16 as willbe hereinafter described.

The sealing ring 14 is made of elastomeric material such as rubber orthe like, and is provided integrally at the rear face or end thereofwith flared lips 14a, 14b for an effective sealing engagement with themissile body 11 and the gun barrel, respectively. The periphery of thering 14 is engraved with helical grooves 14c which are complemental toand slidably engageable with the rifled barrel.

The wedge unit 15, disposed forwardly of the sealing ring 14, ispreferably made of a suitable plastic material and is also engraved onits periphery with helical grooves for sliding engagement with therifled barrel. The inside of the wedge unit is provided with a shoulder18 which is seated in an annular groove 19 formed in the missile body11, whereby to prevent axial displacement of the wedge unit relative tothe missile body. The wedge unit consists of a set of separable,complemental segments, as for example the segments 15a, 15b, and theradial interfaces between these wedge segments are serrated as indicatedat 20 in FIG. 3 so as to provide a labyrinth type seal and prevent gasleakage axially through the wedge unit.

The petal unit 16 is disposed forwardly of the wedge unit 15 and ispreferably made of metal, as for example aluminum. The inside of thepetal unit 16 is provided with a series of load transfer grooves 24which mate with a series of grooves 25 formed in the missile body 1 1 toprevent axial displacement of the petal relative to the missile body.The outer periphery of the petal unit is smooth for sliding engagementwith lands of the barrel rifling, and the petal unit also consists of aset of separable, complemental segments, as for example the segments16a, 16b, 160, as shown in FIG. 1. The radial interfaces between thepetal segments are also serrated, as at 21, to prevent gas leakage.

Preferably, the number of segments in the wedge unit 15 is differentfrom the number of segments in the petal unit 16, so that for purposesof preventing gas leakage, the radial interfaces between the wedgesegments are always circumferentially spaced from the radial interfacesbetween the petal segments. Thus, for example, the wedge unit mayconsist of two segments and the petal unit of three segments.

As an important feature of this invention, the rear of the petal unit 16and the front of the wedge unit 15 have complemental frusto-conicalfaces 22, 23, respectively, slanting forwardly and outwardly as will beapparent from FIG. 2. The aforementioned washer 17 may be interposedbetween these faces 22, 23, and may be radially split to facilitate itsseparation from the missile at the muzzle of the gun barrel, suchseparation of the petal unit 16 and wedge unit 15 also being possible byseparation of the petal segments and wedge segments in each set.

The sealing ring 14, as stated, is made of elastomeric material or thelike and separates due to structural failure at muzzle exit.

The exterior profile of the petal unit 16, the wedge unit 15, and thefront end of the sealing ring 14 are such as to fit a new gun barrel,but the flared lip 14b at the rear of the ring 14 will also seal againsta worn barrel.

When the missile l0 equipped with the sabot 13 is placed in the barreland the gun is fired, the sealing ring 14 provides an initial gas tightseal against both the missile and the barrel. As the missile travelsthrough the gun barrel, gas pressure against the sealing ring 14 exertsa forward axial force on the wedge unit 15 and on the petal unit 16.This force acts through the complemental frusto-conical faces 22, 23 sothat the segments of the wedge unit 15 are urged outwardly against thebarrel while the segments of the petal unit 16 are urged inwardlyagainst the missile, thus centering the petal unit and missile in thebarrel and minimizing ballotting loads. Also, some deformation of theplastic wedge segments occurs and generates a secondary travelling sealagainst the barrel and missile.

In the meantime, the grooved peripheries of the sealing ring 14 andwedge unit 15 slide in the rifled barrel and rotation is thus impartedto these parts. However, the wedge unit 15 slips relative to the petalunit 16 at the washer 17 (or at the interfaces 22, 23 if no washer ispresent), with the result that the petal unit 16 rotates at a lowerrate. The petal unit 16 may rotate upon the missile in turn so that themissile rotates only at an acceptable low rate of spin by residualfriction forces. Finally, at the muzzle exit positive rotation of thewedge unit 15 and acceptably low rotation of the petal unit 16 causesthe petal segments and the wedge segments to separate from the missileby centrifugal force.

In many instances it may be desirable for the rear, finned end of themissile to protrude rearwardly into the propellant charge chamber of thegun, and the sabot must therefore enter barrel rifling during loadingprior to firing. To facilitate this, the groove engraving 150 at theleading edge of the wedge unit 15 is modified by a reverse bevel asshown at 15d in FIG. 4, so that the grooves of the wedge unit areself-indexing upon entering the barrel rifling.

We claim:

'l. A sabot for locating a finned missile in a rifled barrel comprising,in combination:

a rear sealing ring of elastometric material adapted to seal against themissile and having a grooved periphery for slidable sealing engagementwith a rifled barrel;

an intermediate wedge unit disposed forwardly of said sealing ring andalso having a grooved periphery for sliding engagement with a rifledbarrel, said wedge unit comprising a set of separable complemental wedgesegments;

a front petal unit disposed forwardly of said wedge unit for slidingengagement with the lands of a rifled barrel and comprising a set ofseparable complemental petal segments, the rear of said petal unit andthe front of said wedge unit having complemental frusto-conical facesslanting forwardly and outwardly so that the wedge segments may be urgedoutwardly and the petal segments inwardly by a forward axial forceacting on said sealing ring; and

a slip washer interposed between said complemental frusto-conical facesto permit relative rotation of said petal, unit and wedge unit.

2. The device as defined in claim 1 wherein the leading edges of thegrooves of said wedge unit are provided with reversed bevels.

3. The device as defined in claim 1 wherein said sealing ring isprovided at the rear thereof with flared lips for sealing against thebarrel and the missile.

4. The device as defined in claim 1 which is further characterized inthat the number of segments in said wedge unit is different from thenumber of segments in said petal unit, and radial interfaces between thewedge segments are always circumferentially spaced from radialinterfaces between the petal segments.

5. The device as defined in claim 4 which is further characterized inthat said radial interfaces are complementally serrated.

6. The device as defined in claim 1 which is further characterized inthat said petal unit is made of metal.

7. The device as defined in claim 1 which is further characterized inthat said wedge unit is made of plastic material.

1. A sabot for locating a finned missile in a rifled barrel comprising,in combination: a rear sealing ring of elastometric material adapted toseal against the missile and having a grooved periphery for slidablesealing engagement with a rifled barrel; an intermediate wedge unitdisposed forwardly of said sealing ring and also having a groovedperiphery for sliding engagement with a rifled barrel, said wedge unitcomprising a set of separable complemental wedge segments; a front petalunit disposed forwardly of said wedge unit for sliding engagement withthe lands of a rifled barrel and comprising a set of separablecomplemental petal segments, the rear of said petal unit and the frontof said wedge unit having complemental frusto-conical faces slantingforwardly and outwardly so that the wedge segments may be urgedoutwardly and the petal segments inwardly by a forward axial forceacting on said sealing ring; and a slip washer interposed between saidcomplemental frustoconical faces to permit relative rotation of saidpetal, unit and wedge unit.
 2. The device as defined in claim 1 whereinthe leading edges of the grooves of said wedge unit are provided withreversed bevels.
 3. The device as defined in claim 1 wherein saidsealing ring is provided at the rear thereof with flared lips forsealing against the barrel and the missile.
 4. The device as defined inclaim 1 which is further characterized in that the number of segments insaid wedge unit is different from the number of segments in said petalunit, and radial interfaces between the wedge segments are alwayscircumferentially spaced from radial interfaces between the petalsegments.
 5. The device as defined in claim 4 which is furthercharacterized in that said radial interfaces are complementallyserrated.
 6. The device as defined in claim 1 which is furthercharacterized in that said petal unit is made of metal.
 7. The device asdefined in claim 1 which is further characterized in that said wedgeunit is made of plastic material.